Text | An energy and exergy analysis of a microturbine CHP system | 001

An energy and exergy analysis of a microturbine CHP system

Basim M.A Makhdoum

School of Mechanical and Systems Engineering Newcastle University Basim.makhdoum@ncl.ac.uk

Abstract

This paper presents an overview of PhD research work performed to date on modelling and simulating microturbine cycles. Utilising the waste heat energy of microturbine in thermal processes has not been fully exploited in recent studies. The microturbine is a producer of both high grade energy (work) and low energy (heat) that can be recovered for a useful purpose. The following low grade heat energy powered systems have been modelled under ISO ambient conditions (international standard organisation), i.e. 15oC and 1 bar, to utilise the waste heat energy of a 200kW microturbine combined with a single effect absorption chiller, an organic ranking cycle using R245fa (ORC-R245fa) as a working fluid, a multi-effect distillation desalination (MED) and or a thermal vapour compression MED Desalination unit (TVC-MED). The thermal comparison was carried out based on an energy and exergy analysis in terms of electric efficiency, exergetic efficiency, carbon footprint, and energy utilisation factor (EUF). The software package called IPSEpro, has been used to model and simulate the proposed power plants. As a result, utilising the exhaust waste heat energy in single-effect absorption chillier has contributed to stabilise ambient temperature fluctuation, and gain the best exergetic efficiency of 39%, while the EUF has reached 72% and the carbon foot print was reduced by 75% in MED and TVC-MED Desalination respectively.

The results also reveal that TVC-MED is more efficient than traditional MED as its gain output ratio (GOR) is improved by 5.5%. In addition, ORC-245fa generates an additional 20% of the microturbine electricity generation.

1. Introduction

Microturbines are small components of modern electricity generators that burn gaseous and liquid fuels, creating high-speed rotation which in turn operates the generators. Working in small stationary and automotive gas turbine has very much benefited from recent developments in the microturbine process [1]. The vast majority of gas turbines today are jet engines, turboprops or turbo shaft engines. A separate class of industrial gas turbine is used in power generation and other heavy-duty applications [2].

The many applications and advantages of microturbines have helped to create a rapidly increasing market. A handful of these advantages are highlighted as follows. First, the environmental performance of the microturbine is very impressive, thanks to decades of